The present invention relates to metallic flange connection gasket to be located between opposite attractable flanges, the gasket on each of opposite faces thereof exhibiting at least one protruding, circling first ridge, and at least one first valley being adjacent the first ridge.
When two pipes having flanges, or a pipe having flange and a unit or element having a flange, e.g. pump and/or valve with flange, are to be interconnected, there is used gaskets of different types between the flanges in order to make certain that the flange connection becomes tight. There is frequently used gaskets of ductile material such as rubber, fiber composites and not so often metal gaskets having inlays of spun, graphite containing threads. In specific cases there is also used so-called RTJ-couplings where a ring of metal is pressed into grooves in the flanges.
All of the aforementioned types of gaskets have their advantages and disadvantages. Gaskets of ductile materials are cheap, but such materials will over time yield due to the pressure and the flange connection must be re-tightened in order to remain tight, and may therefore have a relatively short life. The types having spun, graphite containing threads are relatively expensive, but are able to tolerate quite high pressures and temperatures. Even these must be re-tightened, but the effect thereof is limited to a few times. RTJ couplings do not require any re-tightening, are quite stable and sustain high pressures and temperatures. These couplings require, however, specially processed flanges, and cannot replace other gaskets without replacement of the flanges. Leakages in flange connections can give serious consequences in connection with demanding applications. Leakages at gas plants and installations can result in fires and explosions, and there have been some negative, serious incidents caused by leakages in flange connections associated with such installations. For subsea pipes related to the oil and gas industry, such leakages may result in long-term pollutions before they are discovered, or result in acute, large leakages.
The following patent publications SU 1141254-A, U.S. Pat. No. 4,109,923-A and DE 814977-C1 are mentioned as other known, relevant technology. A less relevant gasket system is known from GB 2244782-A.
It is from Norwegian patent application 20111571 known a metallic flange connection gasket which has a homogenous material, with a ring-shaped or circular ridge region where the material easily can be caused to pass the flow limit upon the attracting the flanges towards each other, but where the flow moves towards an asymptote down towards the flow limit, because the material becomes larger in area as the force of attraction increases. That novel structure has, however, some technical deficiencies and has proved not to provide satisfactory sealing between flanges. These deficiencies are caused mainly by the material which is intended to yield has no adjacent space to flow or move into, and that the configuration does not take into sufficient consideration that flanges bend to a certain extent upon tightening of interconnection bolts. This results in that the faces of the flanges land on the gasket outside the region of sealing and will lift off from the sealing upon application of further force of attraction. Thus, the connection will experience a gradually increasing leakage upon an increased force of tightening on the bolt connection which is used to attract and interconnect the flanges.